For networks of this type it is important to be able to integrate them with systems that have already been installed, such as a LAN (Local Area Network) based on IP (Internet Protocol) technology and that are located in a corporate realir4 with the possible presence of a PABX type corporate switchboard (Private Automatic Branch eXchange).
All this bearing in mind the fact that networks of this type are typically destined to be employed in a supranational context, given that they are aimed at enterprise-is that have offices and branches in different countries. At least two private radiomobile systems have been proposed, that aim to satisfy, at least partially, the afore-mentioned requirements.
One system, produced by the American company Interwave, is called GSM in A Box or Network in A Box. This system is commercialized in Europe by Nortel Cellular under the trade name Piconode.
Another system is that proposed by the Swedish company Ericsson under the tradename Line of Ericsson GSM On A Net (EGON).
The first system mentioned above (henceforth referred to as Piconode for the sake of brevity) is interconnected via a GSM (Global System for Mobile communication) standard A interface to a corresponding PLMN network (acronym for Public Land Mobile Network) and via a PRI interface to a corresponding PSTN network (Public Switched Telephone Network). In a more recent variation, the interface to the PLMN is made with IP transport (Internet Protocol).
In more recent variations, the manufacturer has positioned the BTS's (Base Transceiver Station) on the 1P network and subsequently the A interface also.
The P:conode solution can produce multi-site, multi-node networks, but not “supra national” networks, i.e. PLMN and/or PSTN networks handled in different ways (usually by different operators) in different countries.
The term “supranational” dearly refers to the context that is currently prevalent in the telecommunications sector, at least at the European level. It should, however, also tie understood to refer to the possibility of interfacing with different PLMN and or PSTN networks connected to different operators within the same country.
To return to the description of the Piconode system, however, one of the main innovations is that a user profile has been introduced to distinguish between public us r, hybrid user and private user.
The pubs is user is only recognized by the public network Home Location Register HLR, the private user only by the Piconode network HLR, while the hybrid user is recognized by both HLR's. Mobility is handled by circuit signaling as per the GSM standard.
The Piconode system does not offer new services that differ from the normal PLMN network, but exploits some of its special characteristics. In particular, it does riot have the capability to interwork with other corporate databases that contain sensitive data.
One interesting aspect of the Piconode system is that it routes calls that originate at its input. This routing is carried out on the basis of information reside::it in tables that can only be changed by the network administrator. The system therefore permits call routing, but not by the user, which means a service called “Incoming Call Screening” (or ICS) cannot be configured Full flexibility is therefore not possible, which is an important factor in the ICS service in a “corporate” environment.
The Ericsson system called EGON is based on the ITU T Recommendation H.32 3, which describes the terminals, the equipment and services for multimedia communication over a packet-based network.
The basic concept of H.323 is that of keeping call control and connection control separate once established.
The EGON solution gives all business users of the corporate Intranet network the opportunity to use the user terminal mobility within the IP network.
One of the main EGON system characteristics is the fact that the corporate Intranet network can be accessed by GSM mobile terminals, IP fixed telephones and personal computers in order to give the corporate users total mobility. Roaming is possible on the GSM public network.
System architecture is based essentially on the presence of three different nodes c filled Service Node, Access Node and Application Node plus two gateway functimialities, Signaling Gateway and Voice Gateway.
The service node is the core of the service and as such is responsible for the following functions:
call setup and routing,
uw er administration, and
handling of security and services offered.
As regards call setup and routing, the service node controls all the ells made between different types of terminals and translates the addresses between different types of access, for example between PSTN telephone numbers and addresses in the system.
User administration has the task of handling all users with registered system identity and service profile. The profile lists all the services to which the user has access.
Management of security and the services offered includes functions of authentication, resource management and least-cost routing. This function includes an API (Application Program Interface) for high-level access and applications (voice mail and fax, e-mail, web-initiated dialling and other vertical applications).
The access node enables GSM mobile terminals to access the system by handling system radio resources and the mobility of the users in the network.
The access node is involved whenever a call is set up to or from a GSM mobile terminal IL The node does not carry any traffic information, but controls communication between the GSM mobile terminals involved. It can interrogate the Home Location Register (MR), manage the roaming numbers and run/control the paging and handover processes.
In terr is of the public GSM network, the access node and its underlying structure are perceived as a Location Area within the corporate network. The application node enables high level applications to interact with the system through an API. Available applications are:
Web-initiated Dialling,
Directory-assisted Dialling
unified messaging service, and
simplified integration with LAN-based business support systems.
The signaling gateway respectively translates between the typical protocol architecture levels on a common channel in circuit-switching mode in the TCP/1:P protocol (Transmission Control Protocol/Internet Protocol) for signaling information transport, and in packet-switching mode within the EGON system IP network.
The voice gateway translates the voice communications between the circuit switching; public networks and the packet-switching private IP type EGON network. The voice gateway is capable of examining fax and voice type calls from the circuit-switching public networks and transfer them in an appropriate format to the packet-switching EGON system IP network. At the same time it is capable of examining voice and fax calls forwarded from terminals inside the EGON system IP network and reconstruct the data flow before transmitting it on the circuit-switching public networks.
One of the critical aspects of the EGON system is the complexity of the IP protocol 1 required to ensure, on the one hand, the physical possibility of performing the multimedia services inside the system, and on the other hand, the presence and co-existence of the fixed and mobile terminals and the network equipment described in ITU-T recommendation H.323.
Another critical aspect is the need to provide a gateway for the translations involving the protocols referred to previously, signaling information and voice and data services that transit between circuit-switching public networks PSTN and PlMN and the packet-switching IP EGON network. This system, in addition, is currently not capable of masking the management of employee mobility between the physical national corporate nodes as they are involved, for the external public networks.
The system is also currently not able to ensure one of the requirements considered important by the corporate customer, i.e. total reachability of an employee, be he/she under public or private domestic coverage or under public or private visited coverage as a roamer user.
Other critical aspects of the system are related to the portability of the integer,. network services based on mechanisms and protocols of the proprietary type between two physical nodes in a physical private supranational network. This apples, for example, for the possible activation of the intelligent services resident in a physical, domestic node from a visited physical node. In other words, the user that is roaming on a physical visited node cannot, from remote, use a set of services based on an intelligent network and located on the domestic node of the corporate network.